• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Peroxide Investigation

Extracts from this document...

Introduction

Sc1 Peroxide Investigation - James Baxter 11AS Introduction This experiment will investigate the effect of an environmental factor on the rate of Hydrogen Peroxide breakdown using Peroxidase enzyme in celery. We will be adding Peroxide (H202), which is a toxic product of several different metabolic reactions, to liquefied celery. The peroxidase enzyme in the liquefied celery has a specific active site like every enzyme and the hydrogen peroxide is a substrate that fits the active site of the peroxidase enzyme. Every enzyme as an active site, like a cleft or depression in its side and this enzyme has a substrate or substrates that fit this cleft exactly. In this experiment the interaction of the substrate (hydrogen peroxide) with the active site on the peroxidase enzyme breaks the substrate apart into two different products - water and oxygen. These two product molecules leave the active site, leaving the enzyme molecules unchanged and ready to bond with another substrate molecule. Hydrogen Peroxide Water + Oxygen 2H202 2H2O + O2 Variables There are many variables that we could change in the proceedings of our experiment that would change the rate of hydrogen peroxide breakdown and they are as follows: - 1) pH - Most enzymes work best at a pH of around neutral (pH 7), however some enzymes have a different optimum pH. Since pH is simply a measure of hydrogen ions and these ions can't interact with the bonding of certain chemicals (for example, amino acids), an enzyme working in a pH very different from its optimum pH will have its bonding interfered with and it will eventually become denatured. We could perform the experiment under a number of different pHs and, keeping all other variables constant, see the effect of pH on the rate of oxygen production, hydrogen peroxide breakdown. 2) Temperature - When temperature is increased, the molecules in a chemical will move faster, thus increasing collisions between the substrate and enzyme, therefore speeding up the reaction. ...read more.

Middle

I divided the 30ml celery solution into five beakers, each containing 3ml of the liquefied celery. I decided this after using 5 divisions of 5ml celery, which produced a reaction slightly too vigorous to produce reliable results. Therefore I decided to use less celery (only 3ml for each of the 5 experiments instead of 5ml) to produce a reaction more under control to give a more reliable set of results. Even though this means that 15ml of the celery is not used, it gives a more controlled experiment than had we divided the celery into 5 beakers of 5ml or 6ml each and used up all or most of the celery solution. Therefore the amount of celery in each beaker should be small rather than large, if a more controlled experiment and a more reliable set of results are desired. 4) Use a syringe to remove one of the celery solutions from one of the beakers and place it inside the conical flask, or alternatively carefully pour it in so as not to lose any celery solution and thus alter the results. 5) Wash the syringe or take a fresh one, then use it to take one of the peroxide solutions and add it to the celery in the conical flask by squirting it down the side of the conical flask. This is necessary to ensure there is no backsplash of the corrosive peroxide. Place the bung into the conical flask quickly so as not to loose any oxygen. The celery should be of 100% concentration, obtained by liquefying the celery into a pureed form. 6) Start the timer and record the amount of oxygen collected in the gas burette at a constant period of time. I decided to time each experiment for five minutes, and measure the amount of oxygen collected every 30 seconds during those five minutes. I came to this decision based on the rate of oxygen production seen in the pilot practical, where a recoding every 30 seconds for 5 minutes seemed to give reliable results and was not too difficult to record. ...read more.

Conclusion

To get reliable results the experiment should be repeated, making sure that there are no foreign factors, especially pH, affecting the experiment. Evaluation The main error of my experiment was the fact that the pH of the hydrogen peroxide solutions did not remain constant and so there were other variables affecting the experiment. This means although while my first experiment gave inconclusive results as to the relationship between peroxide concentration and oxygen production, it concluded that the pH adversely affects the reaction rate as it becomes more acid. This foreign variable (pH level) could be kept constant by neutralizing it and keeping the pH at a constant level, as performed in the second, controlled experiment, and this would give conclusive results about the relationship between peroxide concentration and rate of oxygen production. The air temperature of the room seemed to increase rapidly throughout the experiment, and this would have affected the results by varying the temperature at reaction and thus adversely affecting the results. This could be kept constant by making sure that no external heat sources are altered throughout the investigation, and that the room temperature is also kept constant. This is important since if more than one variable is affecting the reaction, in this case peroxide concentration, pH and possibly temperature, the results become inconclusive to any one of those variables and so the whole experimental results become invalid. These factors should be investigated separately to avoid this, for instance the peroxide concentration and room temperature could be kept constant while the pH of the solution increased/decreased, to see what effect this has on the rate of oxygen production. Overall the main flaw in my experiment was the fluctuation of pH level which increased as peroxide concentration decreased, thus drawing no conclusive results to my aim. This should be prevented my making sure the pH level remains constant and so results drawn will be conclusive to the relationship between rate of substrate-enzyme reaction and hydrogen peroxide concentration. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. Marked by a teacher

    How does the concentration of enzymes affect the breakdown of starch by a-amylase in ...

    4 star(s)

    This means that I will therefore not be able to make an accurate judgment as to what the gradient of the curve is at points in-between the tested concentrations.

  2. Marked by a teacher

    Investigating the breakdown of hydrogen peroxide using celery tissue to supply the enzyme catalyst

    4 star(s)

    and size for the enzyme to change the chemical molecule into another substance, or in a catabolic reaction two new substances. Fair Test To make the experiment a fair test, all the other variables must be kept constant, so that they do not influence the results.

  1. Marked by a teacher

    Beetroot Practical Write up

    3 star(s)

    Ethanol also dissolves lipids, so it would damage the membrane and cause it to become completely permeable. This also contributes to the leakage of the pigment from the cell membrane. Ethanol emulsifies the plasma membrane and therefore pigments are released from the membrane.

  2. An Investigation Into the Effect of Substrate Concentration On the Rate of Enzyme Activity.

    The beads were then rinsed with distilled water to remove any excess calcium chloride and kept in a clean beaker. Beads were chosen that all appeared to be of a similar size. Any odd or distorted beads were discarded. To determine which concentration of hydrogen peroxide were appropriate for the

  1. Investigate how concentration of the enzyme catalase in celery tissue alters the rate of ...

    At the maximum rate, at any given time, all the active sites of the enzymes are being implemented, so increasing the substrate concentration has no further effect on the rate of reaction. See below for a graph explaining this relationship.

  2. WHAT EFFECT DOES SUBSTRATE HAVE ON THE RATE OF RESPIRATION IN SACCHAROMYCES CEREVISIAE?

    Also, 15cm3 of buffer solution is a sufficient amount to dissolve quite a lot of powdered substrate, so forming the substrate solution by addition of the solid substrate should not be an issue for me, at this volume. I have decided to keep the concentration of all substrates constant at 1M.

  1. To investigate the rate at which hydrogen peroxide is broken down by the enzyme ...

    The diagram shows how many extra particles now also have enough energy to react. The blue section of the diagram still represents the particles which do not have enough energy to react when a collision with them occurs. Variables: Catalase is an enzyme which breaks down hydrogen peroxide into oxygen and water.

  2. The effect of Copper Sulphate concentration on Catalase activity on Hydrogen Peroxide.

    It is used so that the oxygen produced by the reaction can pass through the delivery tube, which is submerged into the water contained in it. Conical flask It contains solutions that are used during the course of the experiment I used mine to keep the buffer solution in a safe place.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work